Friend, buddy, pal.  A good mate is the best friend a man can have.  Also used if you don’t know someone’s name. “Mate, you might be a pain but I can’t see through you.”

A metre is about 39 inches, very close to a yard which is 36 inches.

The morning tea break is around 10:30 a.m.

Messing about.  When you muck out stables, you scrape out the mixture of straw and horse dung on the floor.  This mixture is called muck.  Presumably stablehands were a playful group.

Mom. Actually, Mum is pronounced the same as Mom in both Australia and America.  Because the accents are different, it has to be spelt (spelled!) differently.

Emphasizing truthfulness, as if the speaker is taking an oath in court.